The present invention relates to improvements in existing anchor cable release mechanisms utilized in guardrail terminal systems. U.S. Pat. No. 6,109,597 discloses in detail an existing anchor cable mechanism. U.S. Pat. No. 6,109,597 in its entirety is incorporated herein by reference for all purpose.
As will be understood by one of ordinary skill in the art, a cable anchor mechanism is used to transmit tensile forces from the rail element to the anchor or foundation in impacts with the longitudinal face of the guardrails. For end-on impacts into the terminal, the cable anchor assembly must be able to release from the anchor or the rail element; otherwise, the cable anchor assembly will impede the forward movement of the impacting vehicle. U.S. Pat. No. 6,109,597 discloses an anchor cable release mechanism that facilitates quick release of the anchor cable bracket from the W-beam rail element. However, it has been found that when the anchor bracket is released from the W-beam rail element it is lifted away from but generally parallel to the W-beam rail element. This created a condition where the bracket was moved into alignment for impact with the next downstream support post causing additional loads on the impact head and the impacting vehicle. The present invention provides unique tapered slot geometry and angled release ramp surfaces on the bracket which lifts the bracket away from and generally out of parallel alignment with the W-beam rail element. Thus the path of the anchor bracket in the present invention is changed from parallel to the W-beam rail element to a path where the downstream end of the anchor bracket is urged away from a direct hit on the post immediately downstream of the anchor mechanism thereby improving the performance of the terminal.
Special quick release anchor cable bracket attachment bolts have a unique structure to reduce frictional contact forces when the bracket is being released from the guardrail. Opposing flat edges allow for the use of a conventional wrench to attach the bolts to the guardrail while opposing radiused edges reduce adverse interactions of the bolt head with the bracket.
To further enhance the desired path of the downstream end of the bracket away from the rail, the leading edge of the anchor impact surface of the terminal guide tube is tapered to increase the moment on the anchor bracket away from the W-beam rail element. The tapered surface applies force closer to the W-beam rail element on the upstream side of the anchor bracket during impact effectively directing the downstream end of the anchor bracket away from and out of parallel alignment with the W-beam rail element.